Business machine printer having plural print heads

ABSTRACT

A high speed serial printer for business machines preferably comprises a plurality of platens each for backing an associated record receiving medium, a continuous Mobius loop inking ribbon, a carriage movable relative to the platens, and a plurality of print heads mounted on the carriage, each print head having a set of selectively movable printing elements cooperable with the inking ribbon to impactingly print on the medium associated with one of the platens. The print heads are mounted back to back on the carriage in opposing spatial relationship, the print heads being offset with respect to each other and the carriage so that each print head impactingly engages the Mobius loop ribbon along each of two parallel printing paths thereon, in order to effect substantially even ribbon wear and best inking characteristics, regardless of the relative usage of the print heads. Also disclosed are a novel ribbon feed, and two-stage return deceleration of the spring-urged carriage toward its rest position.

[451 Oct. 7, 1975 FOREIGN PATENTS OR APPLICATIONS 1,475,009 2/1967 France................................ 197/1 R Primary Examiner-Clifford D. Crowder Attorney, Agent, or FirmMcCaleb, L'ucas & Brugman [57] ABSTRACT A high speed serial printer for business machines preferably comprises a plurality of platens each for backing an associated record receiving medium, a continuous Mobius loop inking ribbon, a carriage movable relative to the platens, and a plurality of print heads mounted on the carriage, each print head having a set of selectively movable printing elements cooperable with the inking ribbon to impactingly print on the medium associated with one of the platens. The print heads are mounted back to back on the carriage in opposing spatial relationship, the print heads being offset with respect to each other and the carriage so that each print head impactingly engages the Mobius loop ribbon along each of two parallel printing paths PLURAL PRINT HEADS Inventors: Albert L. Eischen, Arlington Heights; George Kolomayets, Chicago, both of I11.

Assignee: Victor Comptometer Corporation,

Chicago, 111.

Filed: Apr. 17, 1974 Appl. No.: 461,606

197/5; 197/1 R; 197/64; 197/68; 197/82; 197/168; 197/183 Int. Cl. B41J 3/42; 8411 19/72; B41] 29/10; B41J 33/10 Field of Search 197/1 R, 5, 64, 68, 70, 197/151,168,183,187, 82

References Cited UNITED STATES PATENTS 681,036 8/1901 Burg 197/5 2,399,788 5/1946 5/1971 11/1971 United States Patent Eischen et a1.

[ BUSINESS MACHINE PRINTER HAVING m m b mdn b aaO .HO H. n d ekmcm le er d 8.3 S S Ww dmm m m omm u .U im 6 .W ww m F tt .ea g 58500 n wfldmw i S@% .J.W i h mm D c h m 6 u 5, mm .m fk de h enf c 0.106.! r.. H 5 0 6 aOn S id bp 7 H .HS 8 w w e 6 mw m I Ji 1 f mw no fl l mmu u EXMXXXXX 7 888 8 666 8 171/111. wwwwww 2 l! 9 .9 1 9 w 9 555515. 2:at? I 7 mum" 3 7 Colombo 3,578,129 Kato et al, 3,621,968 Kondur, Jr........ 3,643,777 2/1972 Anderson et a1. 3,670,861 6/1972 Zenner et a]. 3,821,930 7/1974 Boshinski et al..... 3 825,681 7/1974 Cederberg et a1. 3,838,250 9/1974 Naas et US. Patent 0a. 7,1975 Sheet 1 012 3,910,396

h Sums 40th 200 q QUE: 0M 4M U.S. Pamm 00;. 7,1975 Sheet 2 of2 3,910,396

FIG. 3.

n In BUSINESS MACHINE PRINTER HAVING PLURAL PRINT HEADS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to high speed serial printers for business machines, and, more particularly, to a novel serial printer having a plurality of print heads for simultaneously printing on separated record receiving media.

2. Description of the Prior Art High speed serial printers have been developed to employ a plurality of printing elements or wires in a print head movable translationally and continuously relative to the impression-receiving paper or record receiving medium the wires are selectively moved longitudinally to effect dot impressions on the paper in cooperation with an inking means, preferably an interposed ribbon, to complete a line of printing, with the print head then being returned to a home or rest position, the paper fed to receive a succeeding line of printing, and the ribbon fed to present another portion in active inking position. See, for example, the printers disclosed in US. Pat. Nos. 3,703,949 and 3,758,012.

In a business machine such as a cash register, it has been found desirable to utilize printers for several record receiving media, such an itemized customer receipt, a tally roll or journal stored in the machine for recording essential audit information for all transactions, and a document or slip which may be manually inserted into the side of the machine to receive transaction data.

However, use of a separate high speed serial printer in a business machine for each of several record media is undesirably expensive.

SUMMARY OF THE INVENTION The business machine printer of the present invention provides an inexpensive solution to this problem, and comprises a plurality of high speed serial print heads mounted on a single reciprocably movable carriage, with drive means for moving the carriage relative to a plurality of platens each for backing an associated record receiving medium. The details of such a print head are disclosed in co-pending application for US Pat. Serv No. 313,248, filed Dec. 8, 1972. A solenoid for longitudinally actuating a printing wire or element in such a print head is disclosed in US. Pat. Ser. No. 3,787,791.

The use of a single carriage and drive means for plural print heads effects substantial cost and space savings. The preferred embodiment of the present invention in a cash register contains two such print heads, one print head being operable to print validation or endorsement information on manually insertable documents, the other print head being operable to print both customer receipts and on the tally roll in the same printing plane, both print heads moving simultaneously through a printing excursion.

The present invention further includes an inking means. which may comprise a relatively long endless loop ribbon wound on a storage reel without the use of a known re-inking device, which is generally unsatisfac' tory in operation. The length of the ribbon insures sufficient time for replenishment of exhausted ink supply by capillary action.

The loop ribbon may include a Mobius twist operable to interchange the surfaces of the ribbon, whereby a print head impactingly engages alternate sides of the ribbon. As those familiar with cash registers will appreciate, a printer for customer receipts and a tally roll will be used more frequently than a printer for manually insertable documents; in some business machines, the latter document printer may be omitted entirely. In the preferred embodiment of the present invention, the print heads, being two in number, are offset with respect to each other and the carriage, whereby each of the print heads engages the Mobius loop ribbon along each of two parallel printing paths thereon, the interchange of printing paths being effected by the Mobius twist, in order to effect substantially even ribbon wear and best inking characteristics regardless of the relative print head usage. Furthermore, the Mobius twist increases ribbon fabric life and minimizes ribbon waste and the effects of curling the ribbon by alternately reversing the side of the ribbon in contact with each printing head.

In addition to the foregoing, the business machine printer of the present invention includes ribbon transport or feed means for cyclically unwinding the ribbon from its storage reel, advancing the unwound portion.

of the ribbon past the print heads, and rewinding the ribbon on to the reel, since the use of an endless loop ribbon precludes a conventional ribbon reverse mechanism. The feed means preferably comprises capstan means, stationary belt means having a loop therein frictionally and circumferentially engaging the capstan means for bidirectionally rotating the latter in accordance with movement of the carriage to and from its rest position, a one-way clutch means driven by the capstan means, and pressure roller means engaging the unwound portionof the ribbon, the pressure roller means being unidirectionally driven by the clutch means to advance the ribbon only when the carriage is moved from its rest position through a printing excursion. Thus, substantially even ribbon wear results from advancement of the ribbon in direct proportion to the movement of the carriage through its printing excursion, unlike ribbon advancement during both directions of carriage travel as disclosed inthe previously mentioned US Pat. No. 3,758,012.

Furthermore, the present invention includes means for effecting two-stage return deceleration of the carriage toward its rest position. More specifically, the business machine printer comprises spring means for urging the carriage toward a rest position, electrically energized drive means operable to move the carriage from its rest position through a printing excursion in opposition to the spring means, stationary strobe strip means, optical sensing means movable with the carriage for engagement with the strobe strip means, and proximity switch means closingly engaged by the carriage prior to return of the latter to its rest position, and electrical control means for controlling the energization of the drive means, the optical sensing means being operable to actuate the electrical control means to energize the drive means for decelerating the carriage when the return speed of the latter exceeds a first predetermined value, the proximity switch being operable to actuate the electrical control means to energize the drive means to decelerate the carriage to a second predetermined return speed just prior to the return thereof to its rest position. The first mentioned return speed through the major portion of its return travel is preferably higher than the second return or impact speed. Thus, the carriage is decelerated by electrically con trolled operation of the drive means in order to insure that its return speeds are at audibly and structurally acceptable levels, while its total return travel time is minimized in order to maximize printer efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view which illustrates the basic features of the preferred embodiment of the business machine printer of the present invention, with parts broken away and with the ribbon storage reel removed;

FIG. 2 is a front elevational view showing the ribbon storage reel and the mounting of the print heads on the carriage illustrated in FIG. 1;

FIG. 3 is a vertical sectional view taken substantially along the line 3-3 of FIG. 2, with the ribbon removed;

FIG. 4 is a view similar to FIG. 3, with parts broken away and parts in vertical section, showing mounting details of the print heads;

FIG. 5 is a plan view illustrating the details of the mobius loop ribbon storage reel, taken substantially along the line 5-5 of FIG. 2, with parts broken away and parts in horizontal section; and

FIG. 6 is a perspective view of a simplified Mobius loop which illustrates its operation in interchanging printing paths on the sides thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT As best seen in FIGS. 1, 2 and 3, the preferred embodiment of the business machine printer of the present invention includes a substantially vertical carriage 11 or other suitable transport means, preferably a steel plate, and a plurality of print heads preferably comprising an upper print head 12 and a lower print head 13, both securely mounted to the carriage in vertically opposing spatial relationship. The print heads 12,13 in the preferred embodiment are the same as that disclosed in co-pending application for U.S. Pat. Ser. No. 313,248, filed Dec. 8, 1972, and each incorporates a plurality of wires or printing elements, preferably seven, each element printingly operable longitudinally by a solenoid 14 like that comprising the subject matter of U.S. Pat. Ser. No. 3,787,791.

The present invention further includes a plurality of platens each for backing an associated record receiving medium. As best shown in FIGS. 2 and 3, the preferred embodiment includes an upper cylindrical platen l6 operable to print a customer receipt 17 and a tally roll or journal 18, respectively, in the same horizontal printing plane, the transport means for these media being omitted for simplification. A lower flat platen 19 is provided for backing an optional manually insertablc document 21.

The printer includes an inking means preferably comprising an endless loop ribbon 22 (FIG. 2) and drive means for reciprocably moving the carriage 11 from a left at rest or home position (shown in FIG. 1) through, a rightward printing excursion horizontally relative to the stationary upper platen 16 and the lower platen 19. The print heads 12,, 13 have sets of selectively longitudinally movable printing elements cooperable with the inking means or ribbon 22 to impactingly print on associated record receiving media. As the carriage 11 traverses rightward through its printing excursion, the upper print head 12 sequentially impactingly prints on the customer receipt l7 and the tally roll 18, while the lower print head 13 prints validation and endorsement data on the optionally insertable document 21.

"With reference to FIGS. 1 and 3, rigidly secured to the rear of the carriage 11 are two yokes 23 or other supporting means each having a removable bearing 24 (FIG. 3) housed in an associated recess, each bearing being resiliently retained in its recess by means of a U- shaped retaining wire spring 25 (FIGS. 2 and 3) having 7 ends thereof inserted into horizontal recesses 26 in the upper print head 12 which is mounted adjacent the carriage 11, the lower print head 13 being mounted back to back in flip-flop arrangement with the upper print I head.

As further illustrated in FIG. 1, a horizontal traverse rod or support rail 27 is provided for sliding engage- I ment with the bearings, the rod being rigidly horizontally supportedin a known manner. The rod 27 is operable to guide and support the carriage 11 as it moves from its left rest position printingly rightward, the wire springs 25 serving to resiliently retain the bearings 24 into their associated recesses to, enable accurate printing alignment of the carriage by the rod, the movable bearings being preferred to the use of accurately aligned bearings rigidly secured to the carriage.

Also rigidly secured to the rear of thecarriage 11 is a yoke 28 (FIG. 1) having a cylindrical anchor portion 29 at the .end thereof rigidly secured to theend of an extension spring 31, and also to the end of an elongate flexible band 32 by suitable known connecting means (not shown). The other end of the spring 31 is secured to a portion of the printer frame 33 by means of a hook 34, the spring being looped around a pulley 35 which is horizontally rotatable about a pivot 36. The other end of the flexible band 32 is connected to a take up reel 37 similar to that disclosed in U.S. Pat. No. 3,861,510, issued on Jan. 21, 1975, which discloses a novelpower drive and timing train mechanism for serial printers, the disclosure of which is incorporated by reference herein.

The extension spring 31 urges the carriage toward its left rest or home position against a bumper (not shown), electrically energized drive means being operable to move the carriage 11 from its rest position printingly rightward in opposition to the spring. As shown in FIG. 1, the take up reel 37 is mounted on a shaft 38 supported by plastic bearings 39. An electrically energized magnetic clutch 41, similar to that disclosed in U.S. Pat.'No. 3,854,562, issued on Dec. 17, 1974, is provided for rotating shaft 38 in a forward clockwise direction, as viewed from thefront of the carriage 11, by means of a gear 42 which meshes with a gear 43 driven by a motor (not shown) through a shaft 44,.when the clutch 41 is electrically energized from a known electrical control circuit 45 through conductors 46. As described in detail in the previously mentioned U.S. Pat. No. 3,861,510, the take up reel 37 defines a peripheral cam surface forwindingly receiving the band 32 upon clockwise rotation of shaft 38 in.

response to energization of clutch .41, to translate the carriage 11 rightward Upon de-energization of clutch 41, the carriage 11 is acceleratingly urged by the spring 31 back toward its left rest position. During a rightward printing excursion, selective energization of solenoids 14 effects longitudinal movement of the printing elements of the print head 12. 13 to effect dot impressions on the paper or record receiving media 17, 18, 21 in cooperation with the inking means or ribbon 22, the carriage I1 is then being returned to its rest position and the paper fed (by means not shown) to receive a succeeding line of printing.

With reference to FIGS. 2 and 4, the print heads l2, 13, preferably identical to minimize manufacturing costs. are rigidly interlocked and mounted in opposing spatial relationship and back to back on the carriage, the print heads being offset with respect to each other and the carriage. The print heads I2, 13 are rigidly secured to the carriage II by means of bolts 48 inserted into horizontal recesses 49 in each of the print heads l2, 13, the bolts being secured by associated nuts 51. As best shown in FIG. I, the upper print head 12 comprises two vertical integral flange portions 52 and a metal support plate 53, which are secured to two horizontal studs 54 rigidly attached to the carriage 11, the studs being suitably apertured at their ends engaging flanges 52 for receiving tapered plastic pins 55 or other suitable connectors (FIG. 2). In FIG. I the ribbon 22, shown by dashed lines, is shown overlying the foregoing upper mounting details to illustrate the location of the ribbon relative to the upper print head 12 and its selectively movable printing elements 56.

With reference to FIG. 3, the carriage 11 comprises an integral horizontal portion 57 and an integral vertical bracket 58 connected to integral flanges 59 of the lower print head 13 and a metal support plate 61 associated therewith, by means of plastic connectors 62.

The business machine printer of the present invention further comprises rotatable storage reel means 63 (FIGS. 2 and 5) mounted on the carriage 11 for windingly storing the major portion of the endless loop ribbon 22. As shown in FIG. 1, which illustrates the printer with the reel 63 removed, attached to the carriage II is a support 64 for a shaft 65 for receiving the reel 63.

Guide means are provided for guiding the unwound portion of the ribbon 22 between the print heads 12, 13 and the platens associated therewith. Two horizontal guide posts 66 are integrally formed with the upper print head 12, with similar guide posts 67 being integrally formed with the lower print head 13 (FIGS. 1, 2, 3 and 4). As shown in FIG. 2, ribbon guides 68 are attached to the carriage 11. A U-shaped metal guide bracket 69 (FIGS. 2 and 3) includes two metal ribbon guide posts 71, the bracket being secured to the guide posts 67 of the lower print head 13 by means of screws 72 received by suitable apertures therein.

The printer of the present invention further comprises ribbon spacing or feed means for cyclically unwinding the ribbon 22 from the storage reel 63, advancing or transporting the unwound portion past the previously mentioned guide means, and rewinding the ribbon onto the storage reel. With reference to FIGS. 1

and 3, the feed means includes a capstan means 73 ro- I tatably fastened to the carriage I1, and stationary belt means preferably comprising a cord 74 having a single loop 75 therein frictionally and circumferentially engaging the roller of the capstan means for bidirectional rotation thereof in accordance with movement of the carriage 11 both to and from its rest position, the belt being rigidly secured to stationary sections ,76, 77 of the printer frame at each end of the belt. The feed means further comprises a one-way sprag clutch means (not shown) internal to the capstan means 73 and driven thereby, and pressure roller means comprising a horizontal lower polyurethane roller 78 (FIGS. 2 and 3) unidirectionally driven counterclockwise, as viewed in FIG. 2, by the clutch through a shaft 79 integrally formed with the roller, the roller having teeth therein for engaging the unwound portion of the ribbon. A pressure roller bracket 81 is rotatably mounted on a shaft 82 extending forwardly from carriage 11 (FIG. 2) for urging a horizontal upper polyurethane roller 83 rotatably supported by the bracket and also having teeth therein, into engagement with roller 78 by means of a torsion spring 84 on'shaft 82 having its ends respectively engaging the bracket 81 and a pin 85 on the carriage. Thus, the ribbon 22, which is inserted between rollers 78 and 83, is transported or fed counterclockwise relative to the carriage, as viewed in FIG. 2, only when the carriage 11 is moved forward in its printing mode from its left rest position rightward through its printing excursion, and in direct proportion to the amount of its forward movement, thereby effecting substantially even ribbon wear and best inking characteristics.

In the preferred embodiment of the business machine printer of the present invention, the ribbon 11 is approximately sixty feet long and is oriented into a Mobius loop by twisting one end 180 relative to the other and ultrasonically welding its ends, after winding the major portion thereof onto the spool or reel 63. The Mobius twist is operable to interchange the surfaces of the ribbon. Furthermore, since the upper and lower print heads 12 and 13 are offset with respect to each other and the carriage 11, the upper print head 12 engaging the ribbon 22 along a rear printing path closer to the carriage 11 than the front printing path of the lower print head 13 (as best seen in FIGS. 1 and 3), the Mobius twist interchanges the printing paths, whereby each of the print heads engages the Mobius loop ribbon along eachof two parallel printing paths.

As shown in FIG. 5, which illustrates the details of the storage reel 63, the reel comprises front and rear circular plates 86 and 87, respectively, joined by a hub 88 having a V-shaped peripheral surface to enable unwinding of the ribbon 22 from the inside of the portion thereof wound on the reel. The ribbon 22 is thus positioned in a vertical plane as it is unwound from the storage reel 63, but is then twisted 90 degrees in being pulled over guide posts 66 to present a horizontal printing surface at the upper print head 12.

FIG. 6 illustrates the operation of a Mobius loop in interchanging the ribbon printing surfaces and printing paths thereon. Shown in that figure is a simplified single turn Mobius strip or loop, designated by reference numeral 89, which is similar to that of the ribbon 22, with the exception that the major portion of the ribbon 22 is wound around the storage reel 63. Assuming that the upper print head 12 engages the underside of the loop 89 for printing along a portion 91 (shown by dashed lines) of a rear printing path adjacent the carriage plate 11, the loop will be rotated counterclockwise by the feed means such that the next time that the same segment of the ribbon is presented to the upper print head, the latter will then engage another portion 92 (shown by a solid line) along an originally rear printing path. However, due to the Mobius twist designated generally by reference numeral 93, the sides of the loop 89 will be interchanged, thereby causing the upper print head 12 to engage the loop along a portion 94 (shown by dashed lines) of a front printing path, and finally a portion 95 (shown by a solid line) on the front printing path on the side opposite to that which the upper print head initially engaged. Another complete rotation of the ribbon 89 will cause the same to be presented to the upper print head 12 in its original starting position along the rear path after printing along portions or segments 96 and 97. It is apparent that the upper print head 12 engages the ribbon 89 along each of two (front and rear) parallel printing paths thereon. The inter change of printing paths for the lower print head i3 is accomplished in an identical manner, except that it is using a forward printing path at the same time that the upper print head 12 is using a rearward printing path because of the front-to-rear offset relationship of the print heads 12 and i3. Thus, each print head impactingly engages alternate sides of the ribbon, and prints along each of two parallel printing paths, in order to effect substantially even ribbon wear and the best ribbon inking characteristics regardless of the relative usage of the print heads 12 and 13.

The present invention further comprises means for effecting two-stage return deceleration of the springurged carriage 11 toward its rest position upon completion of its printing excursion. With reference to FIG. 1, a stationary horizontal elongated strobe strip 98 having narrow vertical'transparent slits therein is mounted for engagement with optical sensing means, generally illustrated by reference numeral 99 (FIGS. 3 and 4), movable with the carriage. The optical sensing means assembly 99 comprises a plastic vertical arm 100 (PEG. 3) mounted on the carriage plate 11 to retain a lightemitting diode (LED) the latter being energized from a power source (not shown) through conductors 102, and a light sensor 103 attached to the LED by means of a horizontal arm. The optical sensing means assembly 99 is preferably mounted on the upper print head 12 to engage an integral horizontal guide 304 (FIGS. 1, 2, 3 and 4), the light sensor 103 being fitted into a recess in the print head and shielded by integral vertical side panels 105. The sensor 103 is connected by means of conductors E06 (FIGS. ll, 3 and i) to the electrical control circuit 45 (FlG. ll).

As the carriage ill is accelerated by the spring 31 leftward toward its rest position after the print heads 12, i3 have completed their lines of printing, the optical sensing means 99 monitors the return rate of speed of the carriage by measuring the frequency of light pulses from the LED 1011 through the strobe strip 98 to the sensor 103 in a known mannenthe electrical control circuit 45 being operable to automatically energize the electromagnetic clutch 41 through conductors 46 as required, in order to provide a forward or rightward carriage braking force through the band 32, the take up reel 37 and the shaft 38, in order to decelerate the carriage when the return speed of the latter exceeds a first predetermined value, preferably on the order of inches per second, which represents an audibly and structurally acceptable return velocity for the major portion of the carriage return travel.

With reference to FIG. 1, the carriage lli comprises ana integral arm portion 107 operable to closingly engage (as shown in that figure) a judiciously positioned known proximity switch 108, mounted on a portion of the frame 109, just prior to return of the carriage to its rest position. The proximity switch 108 is connected to,

the electrical control circuit 45 by means of conductors 1 1 for actuating the control circuit to energize the drive b means as required to decelerate the carriage to a second predetermined return speed, preferably on the order of 10 inches, per second, just prior to the return of the carriage to its rest possition, in order to effect a safe impact of the carriage against the bumper (not shown).

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various,

changes may be in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:

ii. A business machine printer comprising: a pair of platens comprising upper and lower vertically separated horizontal printing surfaces for backing associated record receiving media, inking means, a carriage, drive means for moving said carriage horizontally relative to said platens, and a pair of vertically opposing print heads mounted in back-to-back relationship on said carriage, each of said print heads having a set of selectively movable printing elements cooperable with said inking means to impactingly print on the medium associated with one of said platens.

2. The printer of claim 1, and spring means for urging said carriage toward a rest position, said drive means being electrically energized and operable to move said carriage from said rest position through a printing excursion in opposition to said spring means, stationary strobe strip means, optical sensing means movable with said carriage for engagement with said strobe strip means, proximity switch means elosingly engaged by said carriage prior to return of the latter to its rest posi tion, and electrical control means for controlling the energization of said drive means, said optical sensing means being operable to actuate said electrical control means to energize said drive means for decelerating said carriage when the return speed of the latter ex.- ceeds a first predetermined value, said proximity switch means being operable to actuate said electric control means to energize the drive means to decelerate said carriage to a second predetermined return speed just prior to the return thereof to said rest position.

i 3. The printer of claim ll, wherein said inking means comprises an endless loop ribbon, and rotatable storage reel means mounted on said carriage for windingly storing the major portion of said ribbon, guide means for guiding the unwound portion of said ribbon between each said print head and the platen associated there with, and feed means for cyclically unwinding said ribbon from said storage reel, advancing said unwound portion past said guide means, and rewinding said ribbon onto said storage reel, and spring means for urging said carriage toward a rest position, said drive means being operable to move said carriage from said rest position through a printing excursion in opposition to said spring means, and wherein said feed means comprises capstan means, stationary belt means having a loop therein frictionally and circumferentially engaging said capstan means for bidirectionally rotating the latter in accordance with movement of said carriage to and from said rest position, one-way clutch means driven by said capstan means, and pressure roller means engaging said unwound portion of said ribbon, said pressure roller means being unidirectionally driven by said clutch means to advance said ribbon only said carriage is moved through said printing excursion.

4. The printer of claim 3, wherein said ribbon comprises a Mobius loop, whereby each of said print heads impactingly engages said ribbon along each of two parallel printing paths thereon.

5. A business machine printer comprising: a pair of platens comprising upper and lower vertically separated horizontal printing surfaces for backing associated record receiving media, inking means comprising an endless Mobius loop ribbon, a carriage, drive means for moving said carriage horizontally relative to said platens, and a pair of vertically opposing print heads mounted in back-to-back relationship on said carriage, each of said print heads having a set of selectively movable printing elements cooperable with said inking means to impactingly print on the medium associated with one of said platens, whereby opposite edge portions of said ribbon are simultaneously presented, respectively, to said print heads and each of said print heads impactingly engages said ribbon along each of two parallel paths thereon. 

1. A business machine printer comprising: a pair of platens comprising upper and lower vertically separated horizontal printing surfaces for backing associated record receiving media, inking means, a carriage, drive means for moving said carriage horizontally relative to said platens, and a pair of vertically opposing print heads mounted in back-to-back relationship on said carriage, each of said print heads having a set of selectively movable printing elements cooperable with said inking means to impactingly print on the medium associated with one of said platens.
 2. The printer of claim 1, and spring means for urging said carriage toward a rest position, said drive means being electrically energized and operable to move said carriage from said rest position through a printing excursion in opposition to said spring means, stationary strobe strip means, optical sensing means movable with said carriage for engagement with said strobE strip means, proximity switch means closingly engaged by said carriage prior to return of the latter to its rest position, and electrical control means for controlling the energization of said drive means, said optical sensing means being operable to actuate said electrical control means to energize said drive means for decelerating said carriage when the return speed of the latter exceeds a first predetermined value, said proximity switch means being operable to actuate said electric control means to energize the drive means to decelerate said carriage to a second predetermined return speed just prior to the return thereof to said rest position.
 3. The printer of claim 1, wherein said inking means comprises an endless loop ribbon, and rotatable storage reel means mounted on said carriage for windingly storing the major portion of said ribbon, guide means for guiding the unwound portion of said ribbon between each said print head and the platen associated therewith, and feed means for cyclically unwinding said ribbon from said storage reel, advancing said unwound portion past said guide means, and rewinding said ribbon onto said storage reel, and spring means for urging said carriage toward a rest position, said drive means being operable to move said carriage from said rest position through a printing excursion in opposition to said spring means, and wherein said feed means comprises capstan means, stationary belt means having a loop therein frictionally and circumferentially engaging said capstan means for bidirectionally rotating the latter in accordance with movement of said carriage to and from said rest position, one-way clutch means driven by said capstan means, and pressure roller means engaging said unwound portion of said ribbon, said pressure roller means being unidirectionally driven by said clutch means to advance said ribbon only as said carriage is moved through said printing excursion.
 4. The printer of claim 3, wherein said ribbon comprises a Mobius loop, whereby each of said print heads impactingly engages said ribbon along each of two parallel printing paths thereon.
 5. A business machine printer comprising: a pair of platens comprising upper and lower vertically separated horizontal printing surfaces for backing associated record receiving media, inking means comprising an endless Mobius loop ribbon, a carriage, drive means for moving said carriage horizontally relative to said platens, and a pair of vertically opposing print heads mounted in back-to-back relationship on said carriage, each of said print heads having a set of selectively movable printing elements cooperable with said inking means to impactingly print on the medium associated with one of said platens, whereby opposite edge portions of said ribbon are simultaneously presented, respectively, to said print heads and each of said print heads impactingly engages said ribbon along each of two parallel paths thereon. 